Problem with async sorting

Sorting by clicking on headers result in void rows at the top and missing rows in the bottom.

If I inscrease rowcount before sorting, the previously missing rows are visible but in the last rows of the grid.

Thank you for a work around if possible.

TTIWAdvWebGrid 5.11

The problem is the same without async, with or without paging.

I solved my problem by replacing the automatic header sorting  with this simple work around (not asynchronous).
May be you can see better see what's going wrong.

procedure TForm.grdColumnHeaderClick(Sender: TObject; ColumnIndex: Integer);
var  r   : integer;
  grd.RowCount := grd.RowCount*2;
  r := 0;
  while r < grd.TotalRows do
    if grd.Cells[0,r] = ''  then grd.DeleteRows(r,1) else Inc(r);

I have not been able to reproduce this issue.
Can you please provide a ready to run sample project that demonstrates the issue so I can further investigate this?

Sample projects can be emailed to